What is a clamp meter ?

A clamp meter is a handhelp electronic device used to measure electrical currents without the need to physically disconnect the current carrying conductor. It has hinged clamp mechanism that can be opened and placed around a conductor (e.g. wire) to measure the current flowing through it.

There are two types of clamp meters viz. AC clamp meter and AC/DC clamp meter. AC clamp meter measures alternating current (AC) in electrical systems. AC/DC clamp meter measures direct current (DC) in addition to AC.

It is used by electricians and technicians to troubleshoot electrical circuits, to identify faults and to measure current in various electronic devices like transformers, motors and power lines.

Modern clamp meters often come with digital displays which allow users to measure current values in numeric formats. Some advanced models may offer additional features such as voltage measurement, frequency measurement, resistance measurement, temperature measurement and more.

How clamp meter works

The clamp meter works based on principle of EM (electromagnetic) induction. When a current flows through a conductor, it generates magnetic field ("H") around it. The clamp meter is designed to detct this H-field which allows it to measure current without making direct contact with the conductor.

The clamp meter measures large ac currents due to its transformer action. When we clamp the jaws of device around the conductor which is carrying the ac current, the current is coupled into the device. This is very similar to iron core of power transformer. The very small amount of current is taken inside due to number of turns ratio between primary and secondary windings.

If the turns ratio is about 1/1000 and if 1 amp of current is flowing which need to be measured would produce 0.001 amps or 1 mAmp of current at the clamp meter input.

Clamp meter measures any combination of alternating as well as direct current. This includes static dc, charging dc and normal ac. Usually Clamp meter measures DC current with the help of hall effect sensors.

Clamp meter uses

Following are the uses of clamp meter of various types.
• Current Measurement: The primary use of a clamp meter is to measure electric current flowing through a conductor without making physical contact.
• Electrical Troubleshooting: Clamp meters are essential for diagnosing problems in electrical systems such as identifying overloads, short circuits (SCs) and imbalances.
• Load Monitoring: They help in monitoring the load on the circuits to ensure they operate within safe limits and prevent any overloads.
• Motor Testing: They're crucial for testing and maintaining electric motors, measuring current draw and ensuring proper functioning.
• It is also used in energy auditing, circuit Verification, safety checks, process control, power quality analysis, HVAC systems, residential wiring and so on.

Clamp meter Application Note

Clamp meter from FLIR systems has following silent features :
• Model No: EX840 CAT IV
• Built-in non-contact Infrared thermometer with laser pointer
• measurement of rms voltage and rms current
• Peak hold feature which captures inflow of currents & transients.
• It has multimeter functionality which includes measurement of ac/dc voltage, capacitance, resistance, frequency, diode as well as continuity test
• It supports 4000 count backlit display
• It has 1.7 inch jaw openings for support of conductors upto 750 MCM / 500 MCM (2 Nos.)

Clamp meter Manufacturers/Vendors

Following are popular clamp meter Manufacturers/vendors:
• Fluke India
• Extech Instruments
• Amprobe
• Kyoritsu (https://www.kew-ltd.co.jp/)
• Farnell
• AEMC Instruments
• AideTek (https://www.aidetek.com/)

Clamp meters are valuable tools for electrical professionals as they allow non-invasive current measurements. It reduces the need to interrupt circuits or dismantle wiring during testing. However, it's important to use clamp meters correctly and follow the safety guidelines provided in user manual to avoid any potential hazards or inaccurate readings.

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